136 A. p. COLEMAN MARINE AND FRESHWATER BEACHES 



time to leave much impress, and as no fossils occur in them the solution 

 of the problem must remain doubtful. 



That the old sealevel at 350 feet continued into the Ontario basin, 

 and may even have reached its western end, seems very probable, and 

 the fact that marine fossils are very abundant east of Brockville, but 

 have never been found to the west, may be accounted for b}'' the nar- 

 rowing of the lower end of the basin forming a strait not very much 

 wider than the present river and only 100 feet deeper ; so that Niagara 

 and the other rivers flowing into lake Ontario were able to keep the 

 waters fresh, or at least only brackish, in spite of their communication 

 with the enlarged g-ulf of Saint Lawrence. 



It may fairly be asked if the beach -like deposits of sand and gravel 

 and also the stratified cla3^s resembling the Leda clay occurring at 

 higher levels in the region west of the fossiliferous beds may not also 

 be of a marine origin, and geologists who have begun their studies in 

 the maritime provinces, wliere many elevated sea beaches exist, are in- 

 clined to this view. Sir William Dawson, Doctor Ells, and Mr Chalmers 

 have looked on these higher stratified deposits, even up to 1,000 feet to 

 the east of Toronto, as probably marine;^ and Doctor Spencer has de- 

 scribed the Iroquois beach, rising at Brighton and Trenton 275 or 300 

 feet above the beach levels referred to in this paper, as formed in an 

 arm of the sea. This conclusion is a very natural one and tends toward 

 simplicity by avoiding the assumption of an ice-dam ; but the finding 

 of freshwater shells in the Iroquois beach near Toronto seems conclusive 

 as to the character of the water, which could hardly remain fresh or 

 even brackish with an opening 70 or 80 miles wide and 400 feet deep 

 into the inland sea fornied by the enlarged gulf of Saint Lawrence. 



If the Iroquois beach is of freshwater origin, there is no need to prove 

 that the higher beach-like deposits are not marine. It may be that 

 some of them were not even formed in standing water, but are glacial 

 and of a kame-like nature, though this can not be stated positivel}^ 

 without some field work in the region. As seen from the Canadian 

 Pacific railwa}^ the latter view seems probable in at least a few cases. 



Climate, and Age of the marine Beds 



The fossiliferous beds of the Ottawa and Saint Lawrence valleys are 

 sometimes spoken of as interglacial, though they can not be considered 

 interglacial in the same sense as the Toronto formation or other fossilif- 

 erous deposits lying between two sheets of till. They usually rest on 



* Bull. Geol. Soc. Am., vol. 9, p. 214 ; Geol. Survey Can., vol. x, 1897, pp. 68 and C9 A. 



